CHAPTER VIII. CORRECTOR EFFECTS— INTERACTIONS 

 BETWEEN CORRECTORS 



91. Until now the principles of compass adjustment have been con- 

 sidered from a qualitative point of view. In general this is quite 

 !-uliicient since the correctors need merely be moved until the desired 

 amount of correction is obtained. However, it is often valuable to 

 know the quantitative effects of different correctors as well as their 

 qualitative effects. Furthermore, as has been stated previously, all 

 the correctors are not completely independent of each other. Inter- 

 action results from the proximity of the permanent magnet correctors 

 to the soft iron correctors, with appreciable induction effects in the 

 latter. Consequently vmy shift in the relative position of the various 

 correctors will change their interaction effects as well as their separate 

 correction effects. Additional inductions exist in the soft iron correc- 

 tors from the magnetic needles of the compass itself. The adjuster 

 should therefore be familiar with, the nature of these interactions so as 

 to evolve the best methods of adjustment. 



92. Quadrantal sphere correction. — Figure 31 presents the approx- 

 imate quadrantal correction available with different sizes of spheres, 



FlCiUKE 31. 



Gl 



